Process of refining vegetable oils



Oct. 29, 1940. B. Hl THURMAN 2,219,968

PROCESS OF REFINING VEGETABLE OILS Filed Dec. 29, 193,8

CBR/oi 0/1. Dia/mmm fusi/vr www# ' Patented Oct. 29, 1940 'Y G VEGETABLE OILS Benjamin H. Thurman, Bronxvilie, N. Y., assignor to Refining, Inc., Reno, Nev., a corporation of N evada Application December 29, i938, Serial No. 248,357

15 Claims.

In accordance with the present invention, the oil is conditioned for alkali refining and the alkali treating step is carried out so that the soap stock 15 resulting from alkali refining is capable of being treated in a simple manner to recover high quality oil. Any gummy materials such as phosphatides, proteins, resins, etc., are removed as far as practicable before treating the oil with an alkali refining reagent. This conditions the oil so that the soap stock produced is relatively free of such gununy materials. In general, such soap stock is lighter in weight and less compact than soap stock containing gums. The layer of soap stock admixed with oil after a soap stock settling operation is, therefore. greater in depth and contains more entrained oil than in conventional batch rening processes. Because of the absence a of substantial .amounts of gums, however, the oil retained in the soap stock can be easily recovered. Dilution with water or equeous solutions of salts followed by continuous centrifugal separation recovers substantially all of the oil in high 35 quality form, although emulsion difficulties due to the presence of gums are encountered when this operation is attempted with ordinary soap stock resulting in still leaving a substantial quantity of oil in the soap stock. Also, such treat- 40 ment of ordinary soap stock produces a low quality oil usually requiring another refining operation. Since the soap stock produced in the present invention is relatively free of gums, the oil may also be recovered therefrom by solvent ex- 45 traction with oil solvents to produce an oil which is not contaminated with gummy impurities soluble in the solvents, and filtration steps may he employed as part of the solvent extraction with- 50 out blocking the lter elements with gummy materials.

It is, therefore, an object of the present invention to provide a process of refining vegetable oils in which high quality oils are recovered from.

55 the soap stock and rening losses are minimized.

Another object of the invention is to provide a process of refining vegetable oils in which alkali rening is carried out under conditions which will produce a soap stock which is capable of being treated torecover high quality oil. 5 A further object of the invention is to provide a process of refining vegetable oils in which an alkali treating step may becarried on as a batch operation and a soap stock is produced which is capable of being treated to recover entrained oil as high quality oil.

Other objects andadvantagesof the invention will appear in the following description of the invention, given in conjunction with the attached drawing, which is a schematic diagram of an 5 apparatus capablel of carrying out a preferred process.

Referring more particularly to the drawing, a crude oil to be refined may be withdrawn from a` source of supply shown as a tank I0 by a pump I I and delivered through a heat exchange device I2 to amixer I3. The heat exchange device may include a coil I4 through which theol is passed, which coil is positioned in a casing I5 through 25 which any desired. heating or cooling medium may be circulated. A degumming reagent is withdrawn from a source of supply shown as a tank I6 by means of a pump I'I and delivered to the mixer I3. The tanks I0 and I6 may be pro- 30.

`be circulated to bring the oil and degumming reagent to desired temperatures for introduction in the process. The pumps II and Il may be driven by a variable speed motor 20 with a variable speed device 2I positioned between the motor 20 and the pump II in order that proportioned streams of oil and degumming reagent may be delivered to the mixer I3, although any other suitable type of apparatus may be employed. The mixing' device I3 may be any suitable ow mixer, such as a device for injecting the degumming reagent at right angles into a stream of the oil, although a mechanical agitator may be employed.

The degumming reagent, which may be water, causes gummy materials such as phosphatides, proteins, resins, etc., to be precipitated in ,the 50 oil as foots which are capable of being separated by difference in specic gravity. Preferably the mixture of cil and foots with excess water or other degumming reagent is passed through a second heat exchanger 22 similar to the heat 55 exchanger I2 and delivered to a continuous centrifugal `separator 23. This centrifugal separator is preferably of the heated type disclosed in Patent No. 2,100,277, granted November 23, 1937, but may be of any suitable type capable of continuously centrifugally separating precipitated gums from the oil. The precipitated gums, along with excess degumming reagent,are discharged as the heavy eflluent through a spout 24 into a receiver 25. The degummed oil is discharged as the light eiiluent through a pipe 25 and in many cases it is preferabley to pass the degummed oil through a heat exchange device 21 to cool the oil prior to delivering the same into a storage tank 28. The storage tank 28 may be an open tank, but is preferably closed and provided with a vent 29. The prior degumming of the oil conditions the same for the production of a soap stocklfrom which high quality oil maybe recovered asf hereinafter described.

A suitable hnanner of alkali treating the oil is to deliver the\same through a pipe 30 from the tank 28 into' a receptacle or kettle 3| which may be similar to conventional batch refining kettles. Alternatively, the tank 23 may be eliminated and the oil delivered directly into the kettle 3| through a pipe 3|. The kettle 3| may be provided with an agitator 32 driven from any suitable source of power through the pulley or sprocket 33. The kettle may be also `provided with a heating coil 34 through which any desired heating medium may be circulated and may further be provided with a heating jacket 35 through which any desired heating medium can be circulated. Either the heating coil 34 or the heating jacket 35, or both, may be employed, depending upon the oil being treated and the rapidity with which it is desired to heat materials in the kettle 3|. After a body of oil has been placed in the kettle 3|, the agitator 32 is ordinarily started and an alkali refining solution, usually an aqueous solution of caustic alkali 'such as caustic soda, is run in through the .pipe 36 until suicient alkali has been added to neutralize the free fatty acids and provide an excess for color reduction, particularly if highly colored oils are being rened. Agitation is then discontinued, and the soap stock produced by neutralization of the free fatty acids is allowed to settle. When settling of the/soap stock has progressed to the desired extent, clear refined oil may be withdrawn from the kettle 3| through a pipe 31 and delivered by a pump 38 into a receiver 39. The pipe 31 is usually a flexible conduit or is adjustable in length so that substantially all of the clear oil .may be withdrawn from the kettle 3|, leaving a layer of soap stock admixed with neutral oil but relatively free of gums. Y

Suflicient water or an aqueous solution of salt as hereinafter explained may then be run into the kettle through a pipe 40, while the agitator 32 is being rotated until a fiowable mixture of soap stock is produced. The flowable soap stock mixture may then be withdrawn from the kettle 3| by means of a pump 4| and delivered to a mixer 42. Additional water or aqueous salt solution may be withdrawn from a tank 43 by means of a pump 44 and delivered to the mixer 42. The pumps 4| and 44 may be driven by a variable speed motor 45 witha variable speed device 46 between the pump 4| and the motor 45, although other suitable mechanisms may be employed.

The tank 43 may be provided with a heating coil 44 through which any desired heating medium may be circulated in order to bring the temperature of the added water or aqueous solution to a fdesired mixing temperature.

In many operations, itis feasible to add sumcient water in the kettle 3| so that the tank 43,

- pump 44'and mixer 42 may be eliminated and the soap stock mixture from the kettle 3| delivered by from the most effective temperature for centrifufgal separation, but may be eliminated if the temperature of the materials in the kettle 3| is suit- 4 able for centrifugal separation. The added dilutingagent is then admixed with the oil and soap stock just before it enters the centrifugal separator 41. tinuously separates neutral oil from the diluted soap stock, and this oil is discharged as the light eflluent through a 'spout 49 into a receiver 50.

The .soap stock, along with the added water, or

aqueous solution, is discharged as the heavy eiuent through a spout 5| into a receiver 52. The centrifugal separator 41 is also preferably of the heated type above referred to, but may be of any type suitable for separating oil from soap stock.

By removing the gums from the oil prior to alkali relining, substantially no gums are present in the soap stock settled from the oil in the kettle 3|. The absence of gums in this soap stock, however, renders the s'oap stock lighter and more difiicult to settle, so that conventional batch refining of degummed oil is not practicable, unless the oil is-recovered from the soap stock, as large amounts of neutral oil are entrained therewith. 'I'hat is to say, the presence of the gums in the soap stock in conventional batch refining provides for a cleaner separation of the soap stock from the oil in batch refining. However, a considerable amount of oil is entrained in the soap stock, even with the gums present therein, and attempts heretofore made to recover this oil from the soap stock containing the gums have resulted in inferior quality oil. I have discovered that, although a larger amount of oil is entrained with the soap stock, this oil can be recovered as high quality oil by diluting the soap stock and then subjecting the resulting mix-ture to continuous centrifugal separation. By operating. in this manner, substantially all of the oil can be separated from the soap stock as high quality oil, and it is unnecessary to run ythe entire amount of oil being refined through the centrifugal separator The centrifugal separator 41 con- 41, as a large portion of the oil may be withdrawn as high quality rened oil from the kettle 3| through the pipe 31. The capacity of the centrifugal separator 41 or the number of centrifugal separators employed, if more than one is used, can, therefore, be reduced.

It is apparent that some oil will be entrained with the gums separated from the oil in the centrifugal separator 23 and discharged into the receiver 25. It is possible to carry on the degumming step of the process as a batch operation in which the degumming reagent, such as water, is mixedwith the oil in a kettle and the ygums allowed `to settle from the oil. In such the present invention. f

Y In such degumming operations, it has been found that the temperature of mixing the degumming reagent with the o'il for most efficient f precipitation of the gums will depend upon the `high as 25% or even higher.

oil being treated and also the most effective temperature for separating the precipitated .gums from the oil as well as the time of treatment between mixing and separation will depend upon the oil being treated and the temperature of treatment. The heating coil I8 in the crude oil tank I0 may be employed to raise the temperature of the oil and reduce its viscosity until it is a freely fiowing liquid. The heat exchanger I2 may be employed to bring the oil to the desired temperature of mixing. The heating coil I8 in the degumming reagent tank I6 may also be employed to bring the degumming reagent to the sulting mixture to that found most effective for separation in the centrifugal separator 23. This temperature will vary with the nature of the oil being treated and the amount and nature of the degumming reagent employed. This temperature may likewise vary from 70 F. or lower up to 160 F. With certain oils, with which the temperature of mixing and the temperature of separation is the same, the heat exchanger 22 may vbe omitted or employed to provide a treating period between mixing and separation. The degumming reagent may be water alone'or aqueous solutions of weak acids or alkalies or neutral salts as disclosed in my copending application Serial No. 248,355 filed December 29, 1938. The sodium thiosulfate and equivalent solutionstherein disclosed reduce the viscosity of the gums and their use minimizes the amount of oil entralned in the gums. Depending upon the oil being treated, the amount of degumming reagent may bev as low-4 as 1 or 2%, although with other oils the amount of water or other degumming reagent may be as If the temperature of separation in the centrifugal separator 23 is in the upper portion of the range mentioned, it may be desirable to cool the oil by passing the same through the heat exchanger 21 prior to delivering the same to the storage tank 28 or into the kettle 3|. With certain oils containing very small amounts of gums, the amount of degumming reagent may be very small, such that very little oil is entrained in the gums separated from the oil and with other oils in which no subr stantial amounts of gums -are present because of prior degumming operations or the nature of the process by which the oils were produced, the degumming operation of the present invention may sometimes be omitted. V

With most oils, it is preferable to start kettle refining with the oil at a relatively low tempera-I ture, for example, between 70 and 90 F., although with some oils it is possible to mix the alkali therewith at somewhat higher temperatures. With the alkali ordinarily employed, that may be withdrawn from the kettle 3|. sary for most efdcient separation, additional ded to produce a refining loss. The lower the temperatureof the oil in the refining kettle 3l during the mixing and neutralization of the free fatty acids, the less the amount of neutral oil saponied. Itis, therefore, desirable to start the kettle refining operation at as low a temperature as practicable. Agitation of the oil with the alkali solution at these low temperatures ordinarily produces an inseparable emulsion which must be heated in order to produce a break, and this heating may 'be accomplished with either the heating coil 34, or the heating jacket 35, or both. Slow agitation is usually employed during such heating, and 'the heating is continued until the break is produced." Heating and agitation are then discontinued and the soap stock allowed to settle from the oil.

After the clear oil has been withdrawn from the kettle by the pipe 31, sufficient water is introduced through the pipe 40 to produce a owable mixture of soap stock and water. This water may 'be atan elevated temperature corresponding to that of the temperature of the soap stock in the kettle, so that it is unnecessary to further' heat the mixture in the heat exchanger 48. If cold is, caustic alkali, some ofthe neutral oil is saponiwater is employed, it will ordinarily be necessary to raise the temperature in the mixture either by heating with the heating jacket 35 or the heating coil 34 positioned in the kettle or by heating the mixture in the heat exchanger 43. The most effective temperature of. separation in the centrifugal separator 41 will depend upon the natureof the oil and soap stock being processed, but will usually be between 110 and 160 F.,

As the excess caustic alkali employedto neutralize the oil in the kettle 3l continues to attack neutral oil as long as it is in contact therewith,

' and considerable time is required to obtain-maximum settling of the soap stock from the oil in the kettle 3I,` refining losses due to saponification of neutral oil may many times be reduced by settling for a shorter period of time, then removing clear oil from a kettle through the pipe 31 prior to maximum settling of the soap stock. A layer `of soap stock and oil in which relatively large proportions of oil are present is then left in the kettle and by again starting the agitator 32 to prevent further stratification of the soap stock, a pumpable mixture of oil and soap stock If neceswater may be delivered into the kettle through the pipe 44I), or, alternatively, additional water may be withdrawn from the tank 43 and mixed with the flowing stream of oil and soap stock in the mixer 42 prior to centrifugal separation. By

- this procedure the time of settling in the kettle is markedly reduced so that refining losses due to saponification of neutral oil are reduced and `substantially all of the oil remaining in the soap -as sodium chloride, sodium sulfate, sodium silicate, sodium carbonate or equivalent potassium salts, that is to say, the neutral salts of alkali metals or the alkali metal ,salts of weak acids, in order to add weight to the soap stock separated of recovering the oil'from the soap stock free from gums are also practical. For example, it is possible to add an oil solvent, for example, a

eral oil solvent such as gasoline or kerosene, to the mixture of oil and soap stock. In such case, the oil-soap stock mixture diluted with the solivent may be centrlfugally separated to separate the oil and solvent as the light efiiuent and the soap stock as the heavy effluent. The solvent.

may, of course, be recovered from the oil by dis-y tillation,`preferably in a vacuum, and re-used in the process. filtered from the oil solvent mixture and the soap stock residue washed with solvent in order to recover substantially all of the oil. For such solvent treatment of the soap stock, it is advantageous to dehydrate the soap stock-oil mixture, for example, by flowing the same into a vacuum chamber to remove substantially all of the water and any vaporizable impurities contained therein prior to mixing the solvent. Such an operation can be carried out in this manner in a vacuum chamber such as that disclosed in the copending application of Benjamin Clayton, Serial No.

287,999 filed October 31, 1938, and such dehydration process is also advantageous prior to mixing with water or other wetting solution, as also disclosed in said application. It will thus be seen that I have provided an improved process of refining vegetable oils containing gums and free fatty acids, for example, cotton-seed oil, soya bean oil, corn oil, sesame oil, etc.

While I have disclosed the preferred embodiments of my invention, it is Iunderstood'that details thereof may be varied within the scope of the following claims.

. What I claim is: h

1. The process of refining vegetable oils, which comprises, treating said oils to remove gums contained therein, thereafter mixing a. body of said oil with an alkali refining agent and settling the resulting soap stock from the oil to produce a soap stock-oil mixture substantially free of gums, withdrawing refined oil from said settled soap `stock, and thereafter diluting the soap stock and separating additional oil from said soap stock.

2. A process of refining vegetable oils containing gums and free fatty acids, which comprises, continuously mixing a degumming reagent with said oil to precipitate said gums and continuously centrifugally separating said gums from said oil, thereafter admixing a body of said oil with an alkali refining reagent and settling the resulting soap stock from said oil, withdrawing refined oil from said settled soap stock and admixing the remaining soap stock containing entrained oil with a diluting agent, and separating oil from said soap stock.

3. The process of refining vegetable oils, which comprises, treating said oils to remove gums contained therein, thereafter mixing Ya body of said oil with an alkali refining reagent and settling the resulting soap stock from the oil to produce a soap stock-oil mixture substantially free of gums, withdrawing refined oil from said settled soap stock, and thereafter diluting the soap stock with water and separating additional oil from said soap stock.

' 4. The process of refining vegetable oils, which comprises, treating said oils to remove gums contained therein, thereafter mixing a body of said oil with an alkali refining agent and settling the resulting soap stock from the oil to produce a Furthermore, the soap stock may be soap stock-.oil mixture substantially' free of gums, withdrawingreflned oil from said settled soap stock, and thereafter diluting the soap stock with water to form a 'flowable mixture and continuously `centrifugally 'separating additional oil from said soap stockt 5. The process of refining vegetable oils, which comprises, treating said oils'to remove gums contained therein,v thereafter mixing a body of said oil with an alkali refining agent and settling the resulting soap st ock from the oil to produce a soap stock-oil mixture substantially free of gums, withdrawing refined oil from said settled soap stock, andthereafter diluting the soap stock with an aqueous solution of a salt which will not attack the neutral oil and continuously centrifugally separating additional oil from said soap stock.

6. The process of refining vegetable oils, which comprises, treating said oils to remove gums contained therein, thereafter mixing a body of said oil with an alkali refining agent and settling the resulting soap stock from the oil to produce a soap stock-oil mixture substantially free of gums, withdrawing refined oil from said settled soap stock, and thereafter diluting said settled soap stock with an oil solvent and separating additional oil in admixture with said solvent from said soap stock.

'7. The process of refining vegetable oils, which comprises, subjecting an oil which is substantially free of gumming material to treatment including admixing a body of said oil with an alkali refining reagent and settling from said oil a soap stock substantially free of gummy material, and thereafter diluting the soap stock to form a iiowable mixture and separating additional refined oil from saidsoap stock.

8. The process of refining vegetable oils, which comprises, subjecting an oil which is substantially free'of gummy material to treatment including admixing a body of said oil with an alkali refining reagent and settling from said oil a soap stock substantially free of gummy material, and thereafter diluting the soap stock with water to form a flowable mixture and continuously centrifugally separating additional oil from said soap stock.

9. The process of rening vegetable oils, which comprises, subjecting an oil which is substantially free of gummy material to treatment including admixing a body of said oil with an alkali refining reagent and settling from said oil a soap stock substantially free of gummy material, and thereafter diluting the soap stock with an voil solvent and separating said solvent along with additional refined oil from said soap stock.

10. The process of refining vegetable oils, which comprises, subjecting an oil which is substantially free of gummy material to treatment including admixing a b'ody of said oil with an alkali refining reagent and settling from said oil a soap stock substantially free of gummy material, dehydrating said soap stock, and thereafter admixing a diluting agent with said soap stock and separating additional refined oil from said including admixing a body of said oil with an alkali refining reagent and settling from said oil a soap-stock substantially free of gummy mate-v rial, dehydrating said soap stock, and theresoap stock with an oil solvent.

l after extracting additional refined oil from the 6 12. A process of renng vegetable oils containing gums and free fatty acids, which comprises, continuously mixing a degumming reagent with said oil to precipitate said gums and continuously centrifugally separating said gums from said oil, thereafter admixing a' body of said oil with an alkali rening reagent and settling the resulting soap stock from said oil, withdrawing rened oil from said settled soap stock and admixing the remaining soap stock containing entrained oil with a diluting agent and continuously centrifugally separating additional reflned oil from said soap stock.

13. A process of rening vegetable oils containing gums and free fatty acids, which /comprises, continuously mixing a degumming re-- agent with said oil to precipitate said gums and continuously centrifugally separating said gums from said oil, thereafter admixing a body of said oil with an alkali refining reagent and settling the resulting soap stock from said oil, Withdrawing refined oil from said settled soap stock and admixing the remaining soap stock containing entrained oil with suicient water to form a iiow able mixture and continuously centrifugally separating additional refined oil from said soap stock.

14. A process of refining vegetable oils containing gums and free fatty acids, which comprises, continuously .mixing a degumming reagent with said oil to precipitate said gums and continuously centrifugally separating said gums from said oil, thereafter admixing a body of said oil with an alkali rening reagent and settling the resulting soap stock from said oil, withdrawing rened oil from said settled soap stock, admixing the remaining soap stock with an oil solvent, and separating -additional rened oil in solution in said solvent from said soap stock.

15. A process of refining vegetable oils containing gums and free fatty acids, which comprises, continuously mixing a degumming reagent with said oil to precipitate said gums and continuously' centrifugally separating said gums from said oil, thereafter admixing a body of said oil with an alkali rening reagent and settling the resulting soap stock from said oil, withdrawing rened oil from said settled soap stock, subjecting said soap stock to.vacuum treatment to remove water and other vaporizable materials therefrom and thereafter admixing the resulting dehydrated soap stock with a diluting agent and separating additional rened oil from said soap stock.

BENJAMIN H. 'I'HURMAN.

, refining agent is not introduced to a. b y of oil previou DISCLAIMER emessa-Benjamin H. Thum, Brtnxviue, N, Y. PRooEss 0F Emme Vmm- BLE OILS. Patent dated October 29, 1940. Disclaimer filed August 13, 1941,

by the assignee, Reyning, I no. the inventor, said Thaman, assenting. Hereby disclaims, as to all claims a pear-ing in said atent, any'process wherein a sy placed in a kettle em loyed in conventional batch practice and wherein the refining reagent is subse uen y admixed with the said body of oil by mechanical agitation, in accordance w1th conventional batch practice as contradistmguished from stream or flow mixing of the oil and reagent.

[Oficial Gazette September 2, 1.941.] 

